Thin film resistor technology is widely used in the semiconductor manufacturing industry. The prior art methods that are currently available for patterning thin film resistors suffer from the effects of topography on the critical dimensions (CDs) of the thin film resistor. In addition, some prior art methods for patterning thin film resistors create metal “stringers” that are capable of electrically shorting the thin film resistors. For example, consider the structure of the prior art thin film resistor shown below in FIGS. 1-6.
FIG. 1 illustrates a cross sectional view of a prior art semiconductor device 100 comprising a thin film resistor (TFR) 120. To create semiconductor device 100 a substrate of dielectric material 110 was provided as shown in FIG. 1. A layer of thin film resistor (TFR) material 120 was deposited on the dielectric material 110 and then masked (photolithography) and etched. A layer of thin film resistor (TFR) protection material 130 (e.g., titanium tungsten) was deposited over the thin film resistor (TRF) 120. The layer of TFR protection material 130 (and portions of the dielectric substrate 110) were then etched and a first titanium/titanium nitride (Ti/TiN) liner 140 was deposited. Then a layer of tungsten (W) 150 was deposited to cover the first titanium/titanium nitride (Ti/TiN) liner 140.
Then a tungsten etch back process is applied to etch away the tungsten layer 150 down to the first titanium/titanium nitride (Ti/TiN) liner 140. The result of applying the tungsten etch back process is shown in FIG. 2. Spacers (also known as “stringers”) of tungsten material 150 remain adjacent to the vertical edges of the portion of the first titanium/titanium nitride (Ti/TiN) liner 140 that is located over the TFR protection material 130 over the thin film resistor 120.
Then a second titanium/titanium nitride (Ti/TiN) liner 310 is deposited over the first titanium/titanium nitride (Ti/TiN) liner 140 and over the spacers 150 of tungsten material. A metal layer 320 (e.g., aluminum) is then deposited over the second titanium/titanium nitride (Ti/TiN) liner 310. The result of these steps is illustrated in FIG. 3.
Then a metal etch process is applied to etch the metal layer 320. FIG. 4 illustrates the result of applying the metal etch process. The metal layer 320 is etched away. The “stringers” of tungsten material 150 are etched away. The second titanium/titanium nitride (Ti/TiN) liner 310 is also etched away. Except for the “stringers” 140 that remain on ridges of the dielectric material 110 (as shown in FIG. 4) the first titanium/titanium nitride (Ti/TiN) liner 140 is also etched away.
Then a titanium tungsten (TiW) etch process is applied to etch away the TFR protection material 130 over the thin film resistor (TFR) material 120. The result is shown in FIG. 5. The “stringers” 140 of the first titanium/titanium nitride (Ti/TiN) liner 140 shown in FIG. 4 also remain in FIG. 5.
FIG. 6 illustrates a plan view of the prior art semiconductor device shown in FIG. 5. A first end of the thin film resistor (TFR) material 120 is connected to a first metal contact pad 610. A second end of the thin film resistor (TFR) material 120 is connected to a second metal contact pad 620. The ends of the “stringers” 140 are also connected to first metal contact pad 610 and to second metal contact pad 620. The problem is that the titanium/titanium nitride “stringers” 140 electrically short the thin film resistor (TFR) material 120 between the metal contact pads, 610 and 620.
Therefore, there is a need in the art for a system and method that is capable of patterning a thin film resistor in a manner that does not create the problems inherent in prior art methods. In particular there is a need in the art for a system and method for patterning a thin film resistor that is immune to the effects of topography on the critical dimensions (CDs) of the thin film resistor.